CA1045879A - Aggregate photoconductive compositions and elements with a styryl amino group containing photoconductor - Google Patents

Abstract

Abstract Or the Disclosure An improved "aggregate" photoconductive composition and electrophotographic elements containing the same are prepared using from 0.1 to less than about 15 weight percent of a compound having a central carbocyclic or sulfur heterocyclic divalent aromatic ring joined to two amino-substituted styryl radicals through the vinylene groups of the styryl radicals.

Description

1~45879 Field of the Invention This invention relates to electrophotography and in particular to photoconductive compositions and elements.
Description of the Prior Art The process of xerography, as disclosed by Carlson in U.S. Patent No. 2,297,691, employs an electrophotographic element comprising a support material bearing a coating of an insulating material whose electrical resistance varies with the amount of incident electromagnetic radiation it receives during an image- -wise exposure. The element, commonly termed a photoconductive element, is first given a uniform surface charge, generally in the dark after a suitable period of dark adaptàtion. It is then exposed to a pattern of actinic radiation which has the effect of differentially reducing the potential of this surface charge in accordance with the relative energy contained in various parts of the radiation pattern. The differential surface charge or ` electrostatic latent image remaining on the electrophotographic ` e~ement is then made visible by contacting the surface with a i suitable electroscopic marking material. Such marking material `, 20 or toner, whether contained in an insulating liquid or on a dry carrier, can be deposited on the exposed surface in accordance with either the charge pattern or discharge pattern as desired. ; -Deposited marking material can then be either permanently fixed -to the surface of the sensitive element by known means such as heat, pressure, solvent vapor or the like, or transferred to a second element to which it can similarly be fixed. Likewise, the electrostatic charge pattern can be transferred to a second element and developed there.
Various photoconductive insulating materials have been employed in the manufacture of electrophotographic elements.
For example, vapors of selenium and vapors of selenium alloys

-2- ~
- :~, ' ~

1~45879 deposited on a suitable support and particles of photoconductive zinc oxide held in a resinous, film-forming binder have found wide application in present-day document copying processes.
Since the introduction of electrophotography, a great many organic compounds have also been screened for their photo-conductive properties. As a result, a very large number of or-ganic compounds have been known to possess some degree of photo-conductivity. Many organic compounds have revealed a useful level of photoconduction and have been incorporated into photocon-ductive compositions. Among these organic photoconductors arethe triphenylamines as described in U.S. 3,18D,730 issued ~pril 27, 1965, and other aromatic ring compounds such as those des-cribed in British Patent 944,326 dated December 11, 1963; U.S.

3,549,358 issued December 22, 1970 and U.S. 3,653,887 issued April 4, 1972.
Opticallv clear organic photoconductor-containing elements having desirable electrophotographic properties can be especially useful in electrophotography. Such electrophotographic elements can be exposed through a transparent base if desired, thereby providing flexibility in equipment design. Such composi-tions, when coated as a film or layer on a suitable support, also yield an element which is reusable; that is, it can be used to - form subsequent images after residual toner from prior images has been removed by transfer and/or cleaning. Thus far, the selection -of various compounds for incorporation into photoconductive com-positions to form electrophotographic layers has proceeded on a compound-by-compound basis. Nothing as yet has been discovered from the large number of different photoconductive substances tested which permits effective prediction, and therefore selec-tion of the particular compounds exhibiting the desired electro-photographic proper~ies.
. ~'. ~' ' .
~'~

. . - . .

1q~45879 A high speed "heterogeneous" or "aggregate" multiphase photoconductive system was developed by William A. Light which overcomes many of the problems of the prior art. This aggregate photoconductive composition (as it is referred to hereinafter) is the subject matter of U.S. Patent No. 3,615,414 issued October 26, 1971 and is also described in Gramza et. al. U.S. 3,732,180 issued May 8, 1973. The addenda disclosed therein are responsible for the exhibition of desirable electrophotographic properties in photoconductive elements prepared therewith. In particular, they have been found to enhance the speed of many organic photo-conductors when used therewith. The degree of such enhancement is, however, variable, depending on the particular organic photoconductor so used.
Summary of the Invention In accord with the present invention there is provided ; an "aggregate" photoconductive composition containing at least two different organic photosensitive components in solid sol-ution with the continuous phase of the multiphase aggregate composition, one of said components being a non-blue light absorbing organic photoconductor and one of said components being an amount within the range of from about 0.1 to less than about 15 weight percent based on the dry weight of said composition ;~
of a compound having a central carbocyclic or sulfur hetero-cyclic divalent aromatic ring joined to two amino-substituted styryl radicals through the vinylene groups of the styryl radicals.
The improved aggregate photoconductive compositions of the present invention offer a number of advantages. Among others, it has been noted that these compositions provide especially useful reusable photoconductive compositions because of their ability to resist electrical fatigue upon being sub-jected to a large number of repetitive electrophotographic imaging cycles.

1~4S879 In addition, the improved aggregate photoconductive compositions of the invention offer an unexpected enhancement in blue light sensitivity.
Moreover, it has also been found that aggregate photoconductive compositions containing the distyryl-containing aromatic compounds used in the present invention exhibit improved temperature stability. Accordingly, the improved aggregate photoconductive compositions of the invention containing these compounds are useful over a wider range of operating temperatures.
In addition, it has been found that the above - advantages provided by the improved aggregate photoconductive compositions of the present invention are generally obtained without any substantial deleterious effect on the totality of electrophotographic properties which cooperate to produce a useful photoconductive composition.
Description of the Preferred Embodiments -` The term "non-blue light absorbing organic photocon- -ductor" as used herein is defined as a photoconductor which ex-hibits little or no light absorption in the spectral range ex- ~
tending from about 400 to 500 nm. Such photoconductors are ~-typically transparent to visible light and therefore colorless;
or if colored, these materials are a color other than yellow, a ` yellow coloration of course, indicating that blue light is being absorbed. Visible light is defined herein as radiation within -the 400-700 nm. region of the spectrum.
The precise mechanism`(s) occurring in the improved aggregate photoconductive compositions of the invention has not been conclusively established and therefore the present invention should not be limited by any specific theory. However, a number of observations have been made relating to the photoconductive compositions of the invention and are presente~ herein to provide a better understanding of the invention.

~5~

1~45879 In the first place, the photoconductive mechanism(s) which is believed to occur in the improved aggregate photo-conductive compositions of the invention is considered to be different than that which normally occurs in conventional "homogeneous" organic photoconductive compositions. Such homogeneous compositions consist of an organic photoconductor such as a triphenylamine compound in solid solution with a polymeric binder. Typically, a sensitizer is also present in the composition. Photoconduction is believed to occur in a uniformly electrostatically charged homogeneous photoconductive - ;
composition as a result of exposure to radiation of the type to which the organic photoconductor is intrinsically sensitive (or to which the organic photoconductor is made sensitive by the addition of a sensitizer), thereby causing the generation of charge carriers within the organic photoconductor. These charge ~
carriers are then transported through the photoconductive ~;
~` composition to a conductive layer where they are dissipated.
In the improved aggregate photoconductive compositions -of the present invention charge carriers are believed to be generated in the photoconductive composition from within the particles of "aggregate" material contained therein. These particles of aggregate material are generally composed of a co-`~1 crystalline complex of an organic sensitizing dye, such as a pyrylium type dye, and a polymeric material, such as a polycarbonate, and are visible within the photoconductive composition with the aid of a microscope. These aggregate particles are thus dispersed as a discontinuous phase in the photoconductive composition and are not in a solid solution with the remainder of the composition. (Further detail relating to the preparation and composition of these "aggregate" particlesis set forth hereinafter.) . ' .

~.

: ~, ~ : , . . . . :

1~45879 In accord with the invention one or more non-blue light absorbing organic photoconductor(s) is incorporated in solid solution with the continuous phase of the aggregate photoconductive composition of the invention. These materials may aid the above-described aggregate particles in the formation of charge carriers, and it is also believed that the organic photoconductor(s) plays a primary role in the transport of the charge carriers through the aggregate photoconductive composition.
It has been shown, for example, that the photoconductivity, i.e.
electrophotographic speed, of the compositions of the invention when exposed to a white light source is significantly increased by the addition of the organic photoconductor~s~. Without the incorporation of one or more organic photoconductors, the white light speed of the composition is so low that the compositions of the present invention are unacceptable for use in conventional office copier applications.
The distyryl-containing aromatic compound contained in the aggregate photoconductive composition of the invention is used as a "fatigue reducer" and as a "temperature stabilizer". ~
For example, the improved aggregate compositions of the invention ~ -exhibit substantial improvement in resistance to electrical fatigue even when sub~ected to a large number of repetitive imaging cycles at relatively high ambient temperature conditions. In addition, although these distyryl-containing aromatic compounds are known to possess photoconductive properties (as described in the cross-referenced Contois and ~ ;
Rossi Canadian patent application Serial No. 197,318, entitled "Photoconductive Composition and Elements Containing Same" filed April 10, 1974), these compounds are believed to act as a blue light sensitizer in the compositions of the present invention.
That is, these compounds appear to absorb blue light and then, 1q~45879 through some type of chemical, electronic or combined chemical-electronic mechanism, intimately interact with the aggregate particles to generate charge carriers.
The precise reason(s) that the distyryl-containing ; aromatic compounds act as a blue sensitizer in the photocon-ductive composition of the invention are not completely under-stood. Although these distyryl-containing compounds do possess photoconductive properties and exhibit blue light absorption, these factors alone do not account for the enhanced blue sensi-tivity of the aggregate photoconductive compositions of the invention. This is readily demonstrated by the fact that certain -known nitro-substituted triphenylamine photoconductors which also exhibit blue light absorption, such as compounds similar to the nitro-substituted triarylamines shown in U.S. Patent 3,180,730 do not provide the above-described blue sensitization effect when substituted for the distyryl-containing compounds incorpo-rated in the photoconductive compositions of the invention.
Similarly, the precise reason(s) that the distyryl-containing aromatic compounds improve the temperature stability " 20 and act as a fatigue reducer in the aggregate photoconductive composition of the invention is also not fully understood.
However, here again it is known that molecularly much simpler nitro-substituted triphenylamine photoconductive compounds sim-ilar to those shown in U.S. 3,180,730 do not provide these advantages when substituted for the distyryl-containing aromatic compounds used in the aggregate-containing photoconductive compositions of the type described above.
The preferred distyryl-containing aromatic compounds used in the invention may be characterized by the following ;
formul~a:

1~ N-Arl-CH=CH-Ar2-CH=CH-Ar3-N < 3 .

. . ~ . . . .
- .

1¢~45879 The preferred distyryl-containing aromatic compounds used in the invention may be characterized by the following formula:

l~N-Arl-CH=CH-Ar2-CH=CH-Ar3-N < 3 wherein Rl, R2, R3, and R4, which can be the same or different, represent alkyl or aryl radicals including substituted alkyl and aryl radicals;
Arl and Ar3, which can be the same or different, represent an unsubstituted or a substituted phenyl radical having one or more substituents selected from the group consisting of an alkyl, aryl, alkoxy, aryloxy, and halogen substituent; and Ar2 represents a carbocylic or sulfur heterocyclic, mononuclear or polynuclear, aromatic ring typically containing ~; 4 to 14 carbon atoms in the ring such as phenyl, naphthyl and anthryl aromatic groups as well as substituted aromatic groups having one or more substituents selected from the group of substituents defined above as substituents for Arl and Ar3.
Y' 1~ R2, R3, and R4 represent one of the following alkyl or aryl groups:
1. an alkyl group having one to 18 carbon atoms e.g., methyl, ethyl, propyl, butyl, isobutyl, octyl, dodecyl, etc.
including a substituted alkyl group having one to 18 carbons atoms such as a. alkoxyalkyl e.g., ethoxypropyl, methoxybutyl, propoxymethyl, etc., - b. aryloxyalkyl e.g., phenoxyethyl, naphthoxymethyl, phenoxypentyl, etc., ~
c. aminoalkyl, e.g., aminobutyl, aminoethyl, ~-aminopropyl, etc., ~
. 1 . ' _g_ ':
.~ .~

1~45879 d. hydroxyalkyl e.g., hydroxypropyl, hydroxyoctyl, etc., e. aralkyl e.g., benzyl, phenethyl, etc., f. alkylaminoalkyl e.g., methylaminopropyl, methylamino-ethyl, etc., and also including dialkylaminoalkyl e.g., diethylaminoethyl, dimethylaminopropyl, propyl-aminooctyl, etc., g. arylaminoalkyl, e.g., phenylaminoalkyl, diphenyl-aminoalkyl, N-phenyl-N-ethylaminopentyl, N-phenyl-N
-ethylaminohexyl, naphthylaminomethyl, etc., h. nitroalkyl, e.g., nitrobutyl, nitroethyl, nitro-pentyl, etc., i. cyanoalkyl, e.-g., cyanopropyl, cyanobutyl, cyano-j ethyl, etc., and j. haloalkyl, e.g., chloromethyl, bromopentyl, chloro-`~ octyl, etc., k. alkyl substituted with an acyl group having the formula :. ~ O
-C-R
wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, napthyl, etc., lower alkyl having one to eight carbon atoms e.g., methyl, ethyl, propyl, etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having one to eight carbon ` atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy, -I naphthoxy, etc; or 2. an aryl group, e.g., phenyl, naphthyl, anthryl, fluorenyl, etc., including a substituted aryl group such as ~ ~ -a. alkoxyaryl, e.g., ethoxyphenyl, methoxyphenyl, propoxynaphthyl, etc., ':
' , .'' :

'~, ,, ., :
'` ' . : . '' , ~ " ~ ' . ' ' 1~45879 b. aryloxyaryl, e.g., phenoxyphenyl, naphthoxyphenyl, phenoxynaphthyl, etc., c. aminoaryl, e.g. aminophenyl, aminonaphthyl, aminoanthryl, etc., d. hydroxyaryl, e.g., hydroxyphenyl, hydroxynaphthyl, hydroxyanthryl, etc., e. biphenylyl, f. alkylaminoaryl, e.g., methylaminophenyl, methylamino-naphthyl, etc. and also including dialkylaminoaryl, ; 10 e.g. diethylaminophenyl, dipropylaminophenyl, etc.
g. arylaminoaryl, e.g., phenylaminophenyl, diphenyl-aminophenyl, N-phenyl-N-ethylaminophenyl, naphthyl-aminophenyl, etc., ; h. nitroaryl e.g., nitrophenyl, nitronaphthyl, nitroanthryl, etc., i. cyanoaryl, e.g., cyanophenyl, cyanonaphthyl, .
cyanoanthryl, etc., - j. haloaryl, e.g., chlorophenyl, bromophenyl, chloronaphthyl, etc., k. alkaryl, e.g., tolyl, ethylphenyl, propylnaphthyl, etc., and ` 1. aryl substituted with an acyl group having the ~ -formula ;~
-C-R
wherein R is hydroxy, hydrogen, aryl, e.g., phenyl, naphthyl, .; .
etc., amino including substituted amino, e.g., diloweralkylamino, lower alkoxy having one to eight carbon atoms, e.g., butoxy, methoxy, etc., aryloxy, e.g., phenoxy,;naphthoxy,etc., lower alkyl having one to eight carbon atoms, e.g., methyl, ethyl, propyl, butyl, etc. ~-;
"',,"
i -11- - -. ~ . . .

1~45879 Typically, when either Arl or Ar3 represent a substituted phenyl radical the substituents on the phenyl radical are alkyl or aryl groups as defined above for Rl, R2, R3, R4 or also any of the following:
1. an alkoxy group having one to 18 carbon atoms, e.g., methoxy, ethoxy, propoxy, butoxy, etc., 2. an aryloxy group e.g., phenoxy, naphthoxy, etc.; `
and 3. halogen such as chlorine, bromine, fluorine or iodine.
Typical compounds which belong to the general class or distyryl-containing aromatic compounds described herein include the following materials listed in Table I below:

;' .~:.

' , ................. .

1¢~45879 ~ ~

~, : :
o o o o o .,1 ~ o ~ a) o ~ ~ ~ o P~ ~ N C~ ~1 ~D ~ ~
~ O ~ ~ O
rl ~ ~ ~ ~

. .
I
~ O
O tJ~ rl ~1 J,~ ~ N ~1 ~ a) :.
R : ~
m ~
R
~ ~ Z - Z

P
`11 ' ~ ` s c~ c :.~ ~ y ~r 11 ~ ~ :: ~

T ~ ~ ~ ~ ~ ~ Iz z ~ R ~ ~1 ~ 0 :
:
-I I _l rl I 'I ~ m m ~1 o ~r o ~ ~r o ~1 ~ C~ ~
m ~ U~ m m m c~ Q, S, c~ c~

m I ~ m I ~ ... ~ - .
; ~rl mrl ~ c~ c~ ~1 ' a 'D ~ O Q, ~ ~ ~, a s ~ .

H H H
-- H ~-I H
-- H _ ..

:

.~ - . .. . -.
:.

1q~45879 C~
~ o o o O U~ O ~D
~1 a~ o ~ l l ~ ~ ) ~r .,, ~ CO o . ~ Q
_I
:.
tn ~1 _I
~ ~ o ~ ,~, _ O
. ~ ~ er ~C
.,, ~ ~9 ~ ~ m ,~ ~
o ~
C~ o ~ s ~.
~ ~: Z
m s m~ m m~
m ~ C~
z z _1 1I m I I I
oc ~ 3 ,Z 1~
:~ m ,~
' _l o c~ ~ ~ z z '' o a~ ' _ m m~ m~ m ~ Z
~ o ~) ~ I m/
a ~ ~ _l I I ~ ~ c~
I ~ m -:> H H. H
-- ~ HH
~, ;

:;

1~4S879 Compounds which belong to the general class of distyryl-containing aromatic compounds described herein and which are preferred for use in accord with the present invention include those compounds having the structural formula shown above wherein Arl, Ar2 and Ar3 are unsubstituted phenyl radicals or alkyl substituted phenyl radicals having no more than two alkyl substituents, said alkyl substituents containing 1 or 2 carbon atoms. These compounds are preferred because aggregate compositions containing the same exhibit increased blue sensitivity and may also exhibit improved resistance to electrical fatigue and improved temperature stability.
The aggregate compositions used in this invention comprise an organic sensitizing dye and an electrically insulat-ing, film-forming polymeric material. They may be prepared by several techni~ues such as, for example, the so-called "dye first" technique described in Gramza et. al., U.S. Patent No.
3,615,396 issued October 26, 1971. Alternatively, they may be prepared by the so-called "shearing" method described in Gramza, U.S. 3,615,415 issued October 26, 1971. This latter method involves the high speed shearing of the photoconductive composition prior to coating and thus eliminates subsequent solvent treatment, as was disclosed in Light, U.S. 3,615,414 ~ -referred to above. By whatever method prepared, the aggregate composition is combined with the above-described disty~yl-containing compounds and one or more organic photoconductors ;
in a suitable solvent to form an organic photoconductor-con-taining composition which is coated on a suitable support to form a separately identifiable multiphase composition, the heterogeneous nature of which is generally apparent when viewed under magnification although such compositions may appear to be substantially optically clear to the naked eye in the absence of magnification. There can, of course, be macroscopic ~; 5 : "
"

: - : . . : : .: , :
- . . : . :, :, ., ., ,.. .. . ~ . .

1~4S879 heterogeneity. Suitably, the dye-containing aggregate in the discontinuous phase is predominantly in the size range of from about 0.01 to about 25 microns.
In general, the aggregate compositions formed as described herein are multiphase organic solids containing dye and polymer. The polymer forms an amorphous matrix or continuous phase which contains a discrete discontinuous phase -as distinguished from a solution. The discontinuous phase is the aggregate species which is a co-crystalline complex com-prised of dye and polymer.
The term co-crystalline complex as used herein has reference to a crystalline compound which contains dye and polymer molecules co-crystallized in a single crystalline structure to form a regular array of the molecules in a three-dimensional pattern.
Another feature characteristic of the aggregate `
compositions formed as described herein is that the wavelength of the radiation absorption maximum characteristic of such compositions is substantially shifted from the wavelength of the radiation absorption maximum of a substantially homogeneous dye-polymer solid solution formed of similar constituents.
The new absorption maximum characteristic of the aggregates formed by this method is not necessarily an overall maximum for this system as this will depend upon the relative amount of dye in the aggregate. Such an absorption maximum shift in the formation of aggregate systems for the present in-vention is generally of the magnitude of at least about 10 nm.
If mixtures of dyes are used, one dye may cause an absorption maximum shift to a long wavelength and another dye cause an absorption maximum shift to a shorter wavelength. In such cases, a formation of the aggregate compositions can more easily be identified by viewing under magnification.

' :

1~45879 Sensitizing dyes and electrically insulating polymeric materials are used in forming these aggregate compositions.
Typically, pyrylium dyes, including pyrylium, bispyrylium, - thiapyrylium and selenapyrylium dye salts and also salts of pyrylium compounds containing condensed ring systems such as salts of benzopyrylium and naphthopyrylium dyes are useful in forming such compositions. Dyes from these classes which may be useful are disclosed in Light U.S. Patent No. 3,615,414.
Particularly useful dyes in forming the feature aggregates are pyrylium dye salts having the formula~
R

wherein:
R5 and R6 can each be phenyl radicals, including substituted phenyl radicals having at least one substituent chosen from alkyl radicals of from 1 to about 6 carbon atoms and alkoxy radicals having from l to about 6 carbon atoms;
R7 can be alkylamino-substituted phenyl radical having from l to 6 carbon atoms in the alkyl moiety, and including dialkylamino-substituted and haloalkylamino-substituted phenyl radicals;
X can be an oxygen or a suIfur atom; and Z~ is an anion.
The pol!ymers useful in forming the aggregate comp-positions include a variety of materials. Particularly useful are electrically insulating, fllm-forming polymers having an alkylidene diarylene moiety in a recurring unit such as those linear polymers, including copolymers, containing the following moiety in a recurring unit:

' :'.
. - .

-; ~ ; . , .: .:, . . ~.. . ..

~45~379 R8 Rg 11 C--`/~ R

wherein:
Rg and Rlo, when taken separately, can each be a hydrogen atom, an alkyl radical having from one to about 10 car-bon atoms such as methyl, ethyl, isobutyl, hexyl, heptyl, octyl, nonyl, decyl, and the like including substituted alkyl radicals such as trifluoromethyl, etc., and an aryl radical such as phenyl and naphthyl, including substituted aryl radicals having such sub-stituents as a halogen atom, an alkyl radical of from 1 to about 5 carbon atoms, etc.; and Rg and Rlo, when taken together, can represent the carbon atoms necessary to complete a saturated ; cyclic hydrocarbon radical including cycloalkanes such as cyclo-hexyl and polycycloalkanes such as norbornyl, the total number of carbon atoms in Rg and Rlo being up to about 19;
R8 and Rll can each be hydrogen, an alkyl radical of from 1 to about 5 carbon atoms, e.g~, or a halogen such as chloro, bromo, iodo, etc.; and R12 is a divalent radical selected from the following:
O S O O O CH
" " " " " ,3 -O-C-, -O-C-O-, -C-O-, -C-O-CH2-, -C-O-CH-, O O
-CH2-O-C-O-, ~nd -O-P-O-,: .
Preferred polymers useful for forming aggregate crystals are hydrophobic carbonate polymers containing the 1~45879 following moiety in a recurring unit:
.
Rg O
..
-R-C-R-O-C-O-' ~10 wherein:
each R is a phenylene radical including halo sub-stituted phenylene radicals and alkyl substituted phenylene radicals; and Rg and Rlo areas described above. Such compo-sitions are disclosed, for example in U.S.Patent Nos.
3,028,365 and 3,317,466. Preferably polycarbonates containing an alkylidene diarylene moiety in the recurring unit such as those prepared with Bisphenol A and including polymeric products of ester exchange between diphenylcarbonate and ~ 2,2-bis-(4-hydroxyphenyl) propane are useful in the practice `~ of this invention. Such compositions are disclosed in the following U.S. Patents: U.S. 2,999,750 by Miller et al, issued September 12, 1961; 3,038,874 by Laakso et al, issued June 12, 1962; 3,038,879 by Laakso et al, issued June 12, 1962;
3,038,880 by Laakso et al, issued June 12, 1962; 3,106,544 by Laakso et al, issued October 8, 1963; 3,106,545 by Laakso et al, issued October 8, 1963; and 3,106,546 by Laakso et al, issued October 8, 1963. A wide range of film-forming poly-carbonate resins are useful, with completely satisfactory results being obtained when using commercial polymeric materials .. . .
- which are characterized by an inherent viscosity of about 0.5 to about 1.8.
The following polymers are included among the -materials useful in the practice of this invention:

~' .
~ ~ , ' .', :

1'&45879 Table 2 No.Polymeric Material 1 poly(4,4'-isopropylidenediphenylene-co-1,4-cyclohexanylenedimethylene carbonate) 2 poly(ethylenedioxy-3,3'-phenylene thiocarbonate) 3 poly(4,4'-isopropylidenediphenylene carbonate-co-terephthalate)

4 poly(4,4'-isopropylidenediphenylene carbonate) poly(4,4'-isopropylidenediphenylene thiocarbonate) 6 poly(4,4'-sec-butylidenediphenylene carbonate) -- 7poly(4,4'-isopropylidenediphenylene '5 carbonate-block-oxyethylene) 8poly(4,4'-isopropylidenediphenylene carbonate-block-oxytetramethylene) 9poly[4,4'-isopropylidenebis(2-methyl-phenylene)-carbonate]
10 poly(4,4'-isopropylidenediphenylene-co-1,4-phenylene carbonate) 11 poly(4,4'-isopropylidenediphenylene-co-1,3-phenylene carbonate) 12 poly(4,4'-isopropylidenediphenylene-co-4,4'-diphenylene carbonate) 13 poly(4,4'-isopropylidenediphenylene-co-4,4'-oxydiphenylene carbonate) :: 14 poly(4,4'-isopropylidenediphenylene-co-4,4'-carbonyldiphenylene carbonate) 15 poly(4,4'-isopropylidenediphenylene-co- :
4,4'-ethylenediphenylene carbonate 16 poly[4,4'-methylenebis(2-methyl-phenylene)carbonate] ~:
17 poly[l,l ~(p-bromophenylethylidene)bis(1,4-phenylene)carbonate]
18 polyl4,4'-isopropylidenediphenylene-co-4,4'-sulfonyldiphenylene) carbonat~r 19poly[4,4'-cyclohexanylidene(4-diphenylene) carbonate]
.~ :

~' .

1~45879 Table 2 (contlnued) ;
No. Polymeric Material -poly~4,4'-isopropylidenebis(2-chlorophenylene) carbonate]
21 poly(4,4'-hexafluoroisopropylidenediphenyl- :
ene carbonate) 22 poly(4,4'-isopropylidenediphenylene 4,4'-isopropylidenedibenzoate) 23 polyt4,4'-isopropylidenedibenzyl 4,4'- :
isopropylidenedibenzoate) 24 poly[4,4'-(1,2-dimethylpropylidene)di-phenylene carbonate]
poly [4,4'-(1,2,2-trimethylpropylidene)-diphenylene carbonate]
26 poly{4,4'-[1-(~-naphthy~)ethylidene]-diphenylene carbonate~
27 poly[4,4'-(1,3-dimethylbutylidene)-. diphenylene carbonate]
; 28 poly[4,4'-2-norbornylidene)diphenylene carbonate]
29 poly[4,4'-(hexahydro-4,7-methanoindan-5-ylidene) diphenylene carbonate]

.~ . .
~ : ~

~' ' .
. ~.
, .

: ~ .:
.

.
~: . . .
... :~ : . . . , , , . .. , . ~ ~

1~45879 Electrophotographic elements of ~he invention con-taining the above-described aggregate photoconductive composition can be prepared by blending a dispersion or solution of the photoconductive composition together with a binder, when necessary or desirable~ and coating or forming a self-supporting layer with the materials. Supplemental materials useful for changing the spectral sensitivity or electrophotosensitivity of the element can be added to the composition of the element when it is desirable to produce the characteristic effect of such materials. If desired, other polymers can be incorporated in the vehicle, for example, to alter physical properties such as adhesion of the photoconductive layer to the support and the like. A list of various other polymers which may be used may be found in the publication Research Disclosure, Vol. No. 109, ; May 1973, p. 63, in Paragraph IV B of the article entitled "Electrophotographic elements, materials, and processes".
Techniques for the preparation of aggregate photoconductive layers containing such additional vehicles are described ~-in C. L. Stephens, U. S. 3,679,407, issued July 25, 1972, 20 and entitled METHOD OF FORMING HETEROGENEOUS PHOTOCONDUCTIVE - -COMPOSITIONS AND ELEMENTS. The photoconductive layers of the -~
invention can also be further sensitized by the addition of effective amounts of other known sensitizing compounds to exhibit improved electrophotosensitivity.
In accord with the invention, the above-described distyryl-containing aromatic compounds are combined with one or more non-blue light-absorbing organic photoconductors to form the improved aggregate photoconductive compositions of the invention.
The non-blue light absorbing organic photoconductive materials are '.

- : . -:

~lt~45879 ~:

advantageously incorporated by dissolving these materials in the organic solvent dope used in coating the improved aggregate photo-conductive compositions of the invention. As a result these organic photoconductive materia]s are in solid solution with the continuous polymer phase of the multiphase structure of the resultant aggregate photoconductive composition. Incor-poration of these organic photoconductors in the aggregate compositions of the invention advantageously results in significantly increasing the white light electrical speed of the aggregate composition.
Especially useful organic photoconductors which exhibit little or no blue light absorption and which may be incorporated in the improved aggregate compositions of the invention include ` non-blue light absorbing materials selected from the following classes of photoconductors: Arylamine photoconductors including substituted and unsubstituted arylamines, diarylamines, -. . .
nonpolymeric triarylamines and polymeric triarylamines such as those described in Fox, U.S. patent No. 3,240,597, issued March 15, 1966 and Klupfel et. al. U.S. Patent No. 3,180,730 issued April 27, 1965; and polyarylalkane photoconductors of the types described in Noe et. al. U.S. Patent No. 3,274,000, ` issued September 20, 1966, Wilson, U.S. Patent 3,542,547, issued November 24, 1970; Seus et. al. U.S. Patent No. 3,542,544, issued November 24, 1970; and in Rule U.S. Patent No. 3,615,402, issued October 26, 1971. Of course, if desired, other non-blue light absorbing organic photoconductors such as those selected from the various classes of organic photoconductors disclosed in Light, U.S. 3,615,414 may also be incorporated in the aggregate compositions of the invention.
' ~A

~ . . ,. ; , ... ........ ... .

1~45879 The amount of the above-described distyryl-containing compound incorporated into the aggregate photoconductive composi-tions and elements of the invention should be less than about 15 weight percent based on the total dry weight of the resultant aggregate photoconductive compositions.
Particularly useful results are obtained where the aggregate compositions of the invention contains 15 to about 40 percent by weight of one or more non-blue light absorbing organic ' photoconductors and as an additive an amount of the distyryl-i 10 containing aromatic compound within the range of from about 0.1 to about 10 weight percent based on the total dry weight of the resultant composition. As the amount of the distyryl-containing aromatic compound is increased beyond the 15 weight percent level specified herein, the absorption and photoconductive properties of the compo~nd begin to have a substantial effect on the resultant photoconductive composition. In addition, the enhance-ment in electrical fatigue resistance (sometimes referred to in : !
, ` the art as charge regeneration) provided in the present invention ; by use of a relatively small amount of the distyryl-containing ~ compound is impaired as very large amounts of the distyryl-- ~ containing aromatic compound are used (i.e. amounts on the order of about 25 weight percent or more). It has been found that certain especially useful embodiments of the present invention which contain in solid solution with the continuous phase of the aggregate photoconductive composition (a) 25 weight percent or more of one or more non-blue light absorbing organic photo-_ conductors and (b) less than 15 weight percent, preferably 5 to 10 weight percent, of the distyryl-containing aromatic -compounds described herein provide optimum reusable characteristics.

That is, the small amount of the distyryl compound appears to function primarily as a fatigue reducer, temperature stabilizer, -and blue light sensitizer for the particulate co-crystalline ,i ' .
l' , . ....

: , . . .. ~ . ~, . - :
. . - . .. .. . .

1~4S~79 complex incorporated in the aggregate photoconductive com-position as described previously herein and appears to have little or no deleterious effect on the photoresponse of the com-position to visible light outside the blue region, i.e., light having a wavelength of from 500 to 700 nm.
As noted above, the amounts of the non-blue light absorbing organic photoconductors incorporated in the compositions of the invention which produce optimum results in terms of electrical fatigue, speed, and temperature stability are usually within the range of from about 15 to about 40, preferably 25 to -about 40, percent by weight based on the total dry weight of the resultant aggregate photoconductive composition. However, larger and somewhat smaller amounts of these photoconductors may also be used.
Suitable supporting materials on which the aggregate ~ photoconductive layers of this invention can be coated include ; any of a wide variety of electrically conducting supports, for example, paper (at a relative humidity above 20 percent);
aluminum-paper laminates; metal foils such as aluminum foil;
zinc foil, etc.; metal plates, such as aluminum, copper, zinc, -~
brass and galvanized plates; vapor deposited metal layers such as silver, nickel, aluminum and the like coated on paper or conventional photographic film bases such as cellulose acetate, polystyrene, etc. Such conducting materials as nickel can be vacuum deposited on transparent film supports in sufficiently thin layers to allow electrophotographic elements prepared therewith to be exposed from either side of such elements. An especially useful conducting support can be prepared by coating a support material such as poly(ethylene ; 30 terephthalate) with a conducting layer containing a semiconductor dispersed in a resin or vacuum deposited on the support. Such , : .`

, ~ : ... . . .

~45879 conducting layers both with and without insulating barrier layers are described in U.S. Patent 3,245,833 by Trevoy, issued April 12, 1966. Likewise, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of maleic anhydride and a vinyl acetate polymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in U.S. 3,007,901 by Minsk, issued November 7, 1961 and 3,262,807 by Sterman et al, issued July 26, 1966.
Coating thicknesses of the photoconductive compositions on the support can vary widely. Normally, a coating in the range of about 10 microns to about 300 microns before drying is useful for the practice of this invention. The preferred range of coating thickness is found to be in the range from about 50 microns to about 150 microns before drying, although useful results can be obtained outside of this range. The resultant dry thickness of the coating is preferably between about 2 microns and about 50 microns, although useful results can be obtained with a dry coating thickness between about 1 and about 200 microns.
After the photoconductive elements prepared according to the method of this invention have been dried, they can be employed in any of the well-known electrophotographic processes which require photoconductive layers. One such process is the xerographic process. In a process of this type, an electrophoto-graphic element is held in the dark and given a blanket electro-static charge by placing it under a corona discharge. This uniform charge is retained by the layer because of the sub-stantial dark insulating property of the layer, i.e., the low conductivity of the layer in the dark. The electrostatic charge formed on the surface of the photoconductive layer is then .

' ~:

:.; - . . . - . , ~ ~ : - - .
: . ' .:, ' . ' :

:1~45879 selectively dissipated from the surface of the layer by image-wise exposure to light by means of a conventional exposure operation such as, for example, by a contact printing technique, or by lens projection of an image, and the like, to thereby form a latent electrostatic image in the photoconductive layer.
Exposing the surface in this manner forms a pattern of electro-static charge by virtue of the fact that light energy striking the photoconductor causes the electrostatic charge in the light struck areas to be conducted away from the surface in pro- ~
portion to the intensity of the illumination in a particular ~ --area.
The charge pattern produced by exposure is then developed or transferred to another surface and developed there, i.e., either the charge or uncharged areas rendered ;
visible, by treatment with a medium comprising electrostatically responsive particles having optical density. The developing electrostatically responsive particles can be in the form of a dust, i.e., powder, or a pigment in a resinous carrier, i.e., toner. A preferred method of applying such toner to a latent electrostatic image for solid area development is by the use of a magnetic brush. Methods of forming and using a magnetic brush toner applicator are described in the following U.S.
Patents: 2,786,439 by Young, issued March 26, 1957; 2,786,440 by Giaimo, issued March 26, 1957; 2,786,441 by Young, issued March 26, 1957; 2,874,063 by Greig, issued February 17, 1959.
Liquid development of the latent electrostatic image may also be used. In liquid development, the developing particles are carried to the image-bearing surface in an electrically insulating liquid carrier. Methods of development of this type are widely known and have been described in the patent literature, for example, U.S. Patent 2,907,674 by Metcalfe .: ' -27- ~
~, , -,: , . . . . . :
.. ' .- . ' , : .

1C~45879 et al, issued October 6, 1959. In dry deYelopin~ processes, the most widely -used method of obtaining a permanent record is achieved by selecting a developing particle which has as one of its components a low-melting resin. Heating the powder image then causes the resin to melt or fuse into or on the element. The powder is, therefore, caused to adhere per-manently to the surface of the photoconductive layer. In other cases, a transfer of the electrostatic charge image formed on the photoconductive layer can be made to a second support such as paper which would then become the final print after development and fusing. Techniques of the type indicated are well known in the art and have been described in the literature such as in "RCA Review" Vol. 15 (1954) pages 469-484.
The following examples are included for a further understanding of this invention.
Preparation of Distyryl-Containing Aromatic Compounds The distyryl-containing aromatic compounds used in the compositions of the invention may be prepared by known methods of chemical synthesis. Specifically, the compounds used herein are prepared by reacting any of various ; dialkylarylphosphonates with an appropriate aldehyde in the presence of a strong base to give the desired olefin product.
By this procedure, the reaction of p-diphenylaminobenzaldehyde or 4-di-(p-tolylamino)-benzaldehyde with an appropriate bis-phosphonate and two equivalents of sodium methoxide in dimethylformamide solution is used to prepare the distyryl compounds I-VIII listed in Table 1 hereinbefore.
For purposes of illustration the specific reaction procedure used to prepare compound V of Table 1 is as follows: I
To a solution of 6.1 g- of tetraethyl 4,6-dimethyl-m-xylylenediphosphonate and 2.0 g. of sodium methoxide in 50 ml of dimethylformamide is added dropwise at room temperature 9.0 g ~-:,.

1~4S87g of 4-di-p-tolylaminobenzaldehyde in 50 ml of dimethylformamide;
an exotherm to 40C occurs. A solid separates after several minutes and the mixture is stirred overnight at room temperature.
The mixture is poured onto 100 g of ice, and the yellow solid ; is collected, washed with 50 ml of water and air-dried to give 10.5 g of crude product, m.p. 91-102C. Two recrystallizations from dimethyl-formamide gives 4.1 g of compound V in the form of yellow crystals, m.p. 211-215C.
The other compounds of Table 1 are prepared by a similar procedure.
Example l Using aggregate formulation methods as described ; earlier herein, a series of aggregate organic photoconductive compositions are prepared containing two different organic photoconductors. The basic dry formulation of each aggregate photoconductive composition tested is as follows: Bisphenol A polycarbonate (56% by weight) purchased from General Electric Co.) + total amount of organic photoconductor (40-30% by weight) + total amount of 4-di-p-tolylamino-4'[4-di-p-tolylaminostyryl]-stilbene (0-10% by weight) + 4-(4-dimethylaminophenyl-2,6-diphenyl thiapyrylium fluoroborate (3.4% by wt.) + 4-(4-dimethyl-aminophenyl)-2-(4-ethoxyphenyl)-6-phenyl thiapyrylium fluoroborate ..
; (.6% by wt.). Each aggregate composition is prepared as follows: ~-; 4-(4-Dimethylaminophenyl)-2,6-diphenyl thiapyrylium fluoroborate (0.17g) and 4-(4-dimethylaminophenyl)-2-(4-ethoxyphenyl)-6-phenyl thiapyrylium fluoroborate (0.03 g) are dissolved in 15 mls. of dichloromethane. Three grams of bisphenol A polycarbonate are then dissolved in this solution and to this dope is added 2.0 grams (total) of organic photo-conductor and 4-di-p-tolylamino-4'-[4-di-p-tolylaminostyryl]-stilbene. After allowing the dope to stand overnight 12.5 mls.
of dichloromethane is added and the resulting dope is hand .. .: :, . , - . . , ;: ::, ' ' ' - ' :

1¢~45879 coated on a nickel coated conductive support to obtain a dry coating thickness of 9~. Significant increases especially in blue speeds are observed when 4-di-p-tolylamino-4'-[4-di-p-tolylaminostyr~l]-stilbene is combined with conventional organic photoconductors as shown in Table 3.
In this example of the present application Relative E & D Electrical Speeds are reported. The relative H & D
electrical speeds measure the speed of a given photoconductive material relative to other materials typically within the same test group of materials. The relative speed values are not absolute speed values. However, relative speed values are related to absolute speed values. The relative electrical speed (shoulder or toe speed) is obtained simply by arbi-trarily assigning a value, Ro, to one particular absolute shoulder or toe speed of one particular photoconductive material.
The relative shoulder or toe speed, Rn, of any other photocon-ductive material; n, relative to this value, Ro, may then be -calculated as follows: Rn = (An) (Ro/Ao) wherein An is the absolute electrical speed of material n, Ro is the speed value arbitrarily assigned to the first material, and Ao is the absolute electrical speed of thefirst material. The absolute H & D electrical speed, either the shoulder (SH) or toe speed, of a material may be determined as follows: The material is ~ -electrostatically charged under, for example, a corona source un~il the surface potential, as measured by an electrometer probe, reaches some suitable initial value VO~ typically about `~
600 volts. The charge element is then exposed to 3000K
tungsten light source through a stepped density gray scale.
The exposure causes reduction of the surface potential of the element under each step of the gray scale from its initial potential VO to some lower potential V the exact value of which : .
: ' ':
-30- ~

, , , , . : :, . ~ .,, ,.

: - . : .: . . :... ~ . . - .. :

1~45879 depends upon the amount of exposure in meter-candle-seconds received by the area. The results of these measurements are then plotted on a graph of surface potential V vs. log exposure for each step, thereby forming an electrical characteristic curve. The electrical or electrophotographic speed of the photoconductive composition can then be expressed in terms of the reciprocal of the exposure required to reduce the surface potential to any fixed selected value. The actual positive or negative shoulder speed is the numerical expression of 104 divided by the exposure in meter-candle-seconds required to reduce the initial surface potential VO to some value equal to VO minus 100. This is referred to as the 100 volt shoulder speed. Sometimes it is desirable to determine the 50 volt shoulder speed and, in that instance, the exposure used is that required to reduce the surface potential to VO minus 50.
Similarly, the actual positive or negative toe speed is the numerical expression of 104 divided by the exposure in meter~
candle-seconds required to reduce the initial potential VO to an absolute value of 100 volts. Again, if one wishes to deter-mine the 50 volt toe speed, one merely uses the exposure required to reduce VO to an absolute value of 50 volts. An apparatus useful for determining the electrophotographic speeds of photoconductive compositionsis described in Robinson et al., U.S. Patent No. 3,449,653 1ssued ~une 10, 1969.

, ,~ .~' .

. . - . . -~ , , :- :
`:
.. . .

1'~4587'3 :
u~ a~
~, ~ o *
u~ u~ o o o o ~ In o o o o ~ U~
a~ ~ ,, ~ ~ ~1 ~1 o a E~ ~ ~
~ .,, ~ a~ ~ ' 1 o O a) _ :
~, o +
o ~
~ ~ u~ o ~ o o In o .,~ ~ o ~ ~ o ~ ~ .,, U~ ~ ,, ~ ~ ~ ~ ~ "
U~
,~
~ E~ ~

U~ id ~, , o ~
~ _ ~o ~ ~ ~ ,, e ~o ~o ~ ~o e ~ a) -:
E~~ ~1 o ~ o ~ o ~n o ~ ~ ~ ~ e C) ~ ~ .,.
s~ 3 O O rl ~
~-~ ~ ~ ~ ~ O ,.,.,:.': ,-~_ L: ~ h ~1 : rl ~ .,1 ~1 ~ O
_~

. ~ ' .
., , .

~:: t~
R l rl ::
q~O I ~ ~1 0 1 U~ .
e ~ o ~ ~ ~
o I ~ o ~, ~~ I ~O U~ O O ~ I ~ O U~ O .~, h~1 ~ :~ _I h --I ~ ~ ~1 h O I h a) O I h t~
Q~~ rl ~ ~ ~J-~ h I ~ ~ I ~ ~ ~ ~
~ Q ~ ~ I ~O ~ ~1 SI ~ O ~ I '~' O R Q
~ t~ ~1 h ,~ ~ ~
* ' '-'' '"

..~ . . .
, 1~P45879 Example 2 Three transparent photoconductive films containing aggregate photoconductive compositions are prepared similar to certain of the films of Example 1. The electrophotographic sensitivity of these films (evaluated as the inverse sensitivity of the exposure requried to discharge the film from 500 v. to 100 v.) is determined as a function of wavelength for all electrophotographic modes, positive and negative surface charging and front and rear exposure. In addition, absorption spectra for each of the three films is recorded and evaluated. ,~
; Each of the three films tested is identical except for the particular aggregate photoconductive composition used in each film. Each of the aggregate photoconductive compositions ~
of the three films contains a particulate co-crystalline comple~ ~ -of a thiapyrylium dye and Lexan~3polycarbonate as a discontinuous phase dispersed in a continuous polymer phase composed of Lexan~
polycarbonate. The particular thiapyrylium dye used in each of the three films is 2~6-diphenyl-4-tp-dimethylaminophenyl) :.
thiapyrylium fluoroborate and the total amount of dye contained in each composition is 3% by weight based on the total dry weight of the aggregate photoconductive composition used in each film. The total amount of Lexan~ polycarbonate contained in each of the photoconductive compositions used in the films is 57% by weight.
A. The remaining 40% by weight of the aggregate photoconductive composition of Film No. 1 (which is a control outside the scope of the present invention) is composed entirely of the organic photoconductor 4,4'-bis-diethylaminotetraphenyl--methane (TPM) which is in solid solution with the Lexan~polycarbonate contained in the con-tinuous phase of the photoconductive composition - .

~ . ' 1 -, l~S879 of Film No. 1.
B. The remaining 40% of the aggregate photoconductive composition of Film No. 2 (which is within the scope of the present invention) is composed of 30% by weight of TPM and 10% by weight of com-pound II of Table 1 of the present application as an additive. The TPM and compound II used in Film No. 2 is in solid solution with the Lexan~
polycarbonate contained in the continuous phase of the photoconductive composition of Film No. 2.
C. The remaining 40% of the aggregate photoconductive composition of Film No. 3 ~which is also a control outside the present invention) is composed of 30%
by weight of TPM and 10% by weight of ditolyl-p-`` nitrophenylamine (DTN). DTN is a yellow appearing prior art compound known to have photoconductive ;
properties and also known to absorb blue light.
` The TPM and DTN used in Film No. 3 is in solid solution with the Lexan~ polycarbonate contained in the continuous phase of the photoconductive --composition of Film No. 3.
The absorption spectra of Film Nos. 1-3 reveals that Film No. 1 possesses a "window" to blue light, i.e., visible light having a wavelength of from about 400-500 nm. That is, Film No. 1 exhibits very little absorption of blue light. Film No. 1, however, readily absorbs visible light having a wave-length within the spectral range of from about 500-700nm. Film Nos. 2 and 3 exhibit an absorption spectra similar to Film No. 1 with respect to visible light having a wavelength within the spectral range of from about 500-700 nm. However, in contrast to Film No. 1, Film Nos. 2 and 3 also absorb blue light so that .
., ' ' .. - ' : , ,: , .. ,. . , ,. ~ :~ -S8~9 the blue "window" of Film No. 1 does not appear in either Film No. 2 or 3.
The electrophotographic sensitivity of each of Film Nos . 1-3 reveals that both controls, i.e., Film Nos. 1 and 3, exhibit rather poor electrophotographic sensitivity when ex-posed to blue light but exhibit good and substantially similar electrophotographic sensitivity to visible light having a wavelength extending from about 500-700 nm. Film No. 2 of the present invention, however, exhibits good electrophotographic sensitivity to blue light. Film No. 2 also exhibits good electrophotographic sensitivity to light having a wavelength extending from about 500-700 nm. Except for the increased electrophotographic sensitivity to blue light exhibited by Film No. 2 of the present invention, the electrophotographic sensitivity of Film Nos. 1-3 to light having a wavelength within the range of from 500-700 nm is quite similar.
The results of the tests shown in this example indicate that the blue sensitization capability of aggregate photoconductive compositions containing compound II of Table 1 (which is representative of the distyryl-containing aromatic compounds of the present invention) is a unique effect and cannot be obtained simply by substituting other known blue absorbing organic photoconductors, such as DTN, for compound II.
Of perhaps even greater significance are the additional test findings that when temperature stability and electrical fatigue tests are run on Film Nos. 1-3, the results show that Film No. 2 (which contains as an additive one of the distyryl-containing aromatic compounds used in the present invention) exhibits substantially better resistance to electrical fatigue and substantially better temperature than either Film No. 1 or 3. For example, Film No. 2 appears to provide good reusable .
. - . ~ - ' - : . ' . ~ . . . :
- . , :. .

.. , . . , . , ~ ... . .. .. ::
. . . .. . . . . . . ..

1~4S~
electrophotographic imaging characteristics similar to room temperature (ie. about 28C) imaging characteristics up to temperatures approaching 65-70C. In contrast, the electro-photographic imaging characteristics of Film Nos. 1 and 3 begins to fall off quite noticeably at a temperature of about 55C in comparison to the normal room temperature (about 28C) imaging characteristics provided by these same films.
Example 3 ; To further illustrate certain of the preferred aggregate photoconductive compositions of the present invention, a 500 cycle electrical regeneration test and an evaluation of relative white light speed is performed on a series of three aggregate photoconductive elements to determine optimum amounts of the distyryl-containing aromatic compound to be incorporated therein for use as an additive. These elements are prepared having coated thereon an aggregate photoconductive composition containing the following materials expressed in weight percent:
~, Bis-phenol A polycarbonate (56%) purchased from General ; Electric Co. under the trademark Lexan~ 145; 4-(4-dimethylamino-phenyl)-2,6-diphenyl thiapyrylium hexafluorophosphate sensitizing dye salt (4%); and the remaining 40% of each com-` position is as shown in Table 4. Each of the three aggregate photoconductive elements is prepared by coating the a~ove-described aggregate composition on a conductive film support to obtain a dry coating thickness of about 9 microns. The aggregate photoconductive compositions coated on each of the three elements tested has an identical composition as indicated ' above except as shown in Table 4 hereinafter.
~; The evaluation of white light speed used in this ` 30 example is carried out by subjecting each of the three aggregate photoconductive compositions for equal times to an identical source of white light radiation using a lens system which is , ::
' ~' .. . , . . . :
. . . . . . . . . . .

1~45879 e~uivalent to a photographic f-number of f/ll. Before the f~ll light exposure, each of the three compositions is ~iven in the dark a uniform negative charge level of -500 volts. Accord-ingly, the composition which exhibits the highest white light speed in this test is the composition which most completely discharges to the zero charge level.
Each cycle of the 500 cycle electrical charge fatigue ; test carried out on these three aggregate elements comprises the steps of (a) subjecting the element to an initial uniform charge, Vo, in the dark of -500 volts, imagewise exposing the uniformly negatively charged surface of the elementto white light using a Xenon flashlamp to form an imagewise charge pattern on the surface of the element corresponding to the original light image pattern, and erasing the imagewise charge pattern by a uniform light exposure of the charge-bearing surface of the element. Since only the electricalPrOpertieS of each element are being tested no development of the charge pattern or transfer thereof is carried out. After completing 500 , repetitions of the foregoing cycle, the ability of the photo-¦ 20~ conductive element to accept completély the initial charge, ~) Vo, of -500 volts is measured. If the element retains its ability to accept completely the -500 volt charge, no electrical ~; fatigue is measurable; therefore the difference in initial charge acceptance capability, ~Vo as set forth in Table 4, is zero. If after completing the 500 repetitions of the fatigue test, the photo-i conductive element is no longer capable of completely accepting the ¦ full initial charge of~500 volts, the amount of charge it does ac-; cept is measured and the difference between this value and the in-itial -500 volts, ie.aVo, is calculated and appears under the col-umn ~Vo in Table 4. As indicated in Table 4 an element containing j an aggregate photoconductive composition which has only a conven-t tional photoconduc~or known to be useful in aggregate photo-:.

: . . . - . ~

1~4S~379 conductive materials (i.e. bis(4-diethylamino)tetraphenyl methane) exhibits a ~Vo of -25 volts indicating that it de-finitely experiences significant electrical fatigue when sub-jected to repeated re-charging and re-exposure. This fatigue characteristic is, of course, disadvantageous for any such photoconductive element contemplated for use as a reusable photoconductive element. In contrast, as Table 4 clearly shows, when an amount of compound II of Table 1 is added to the aggregate photoconductive elements tested in this example, the amount of electrical fatigue as meausred by the foregoing 500 cycle test is substantially reduced=-- ultimately no measurable fatigue is obtained as the amount of compound II
of Table 1 added to the aggregate photoconductive compositions tested in this example is increased. However, as is also shown in Table 1, the element which exhibits little or no measureable -. ~
` fatigue also shows a white light speed loss relative to the - -elements containing lesser amounts of compound II. Thus in accord with the invention, the amount of the distyryl-containing compound wh~ch shouldbe added to obtain an optimum reusable aggregate photoconductive composition should be less than about 15 weight percent.

~ .
:

. ''~ , ~ . .

." ''-' ~

"' " - . ', ' .'.'. . ,'' ' ~''' ' ',," ','' ;~,"', `, '~ ,"' '" ' ~- . , . .. :, ,.. ~ : ~

lr~4~879 ul ~ o r- ~D
~ l l ~

U~
~1 ~n o E~ ~ I
U~
~ ~ E~ ~ .

HG~ ~ H ~1 ~C 1 t~~ ~ ~ o o o E~
0 4-1~: O 11~ _I N --I
: ~~1 0 ~ ~:
u~a) o ~ a) ~~ ~3 C~ O S
1~ ~ ~
$
,1 ~ O O
O
~ ~ O ~ Or~
R ~n * ~ a) ~ ~ a) ~
~: :
OO ~ ~ O O rl O O-rl G~ ' ~-~l o ~ -- -- ,l : :
,.
~ o o o o ~ ~ ~ er rl o~ ~ o - :
o .,l ~
Q) OO O ~ Q
C) ~ *

,, :

~'.
::

:: . ~ . -. . - :- , , 1'~45879 The invention has been described in detail with particular reference to preferred embodiments thereof but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. :

,. ~ , . . ..

- : , ' , ~ ~.

Claims (11)

1. We claim:
   l. An aggregate photoconductive composition comprising (a) a continuous electrically insulating polymer phase, (b) a discontinuous phase comprising a co-crystalline com-plex of (i) a polymer having an alkylidene diarylene moiety in a recurring unit and (ii) a pyrylium dye salt selected from the group consisting of thiapyrylium, selenapyrylium, and pyrylium dye salts, said discontinuous phase dispersed in said continuous phase, (c) at least one non-blue light absorbing organic photo-conductor in solid solution with the continuous phase of said composition, and (d) from about 0.1 to about 15 weight percent based on the dry weight of said composition of a compound having the formula wherein R1, R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said compound in solid solution with the continuous phase of said composition, said aromatic radical containing about 4 to 14 carbon atoms in the aromatic ring thereof.
2. 2. An aggregate photoconductive composition comprising (a) a continuous electrically insulating polymer phase, said polymer having an alkylidene diarylene moiety in a recurring unit, (b) a discontinuous phase comprising a co-crystalline complex of (i) a pyrylium salt selected from the group consisting of thiapyrylium, selenapyrylium, and pyrylium dye salts and (ii) a carbonate polymer having an alkylidene diarylene moiety in a recurring unit, said discontinuous phase dispersed in said continuous phase, (c) at least one non-blue light absorbing organic photoconductor in solid solution with the continuous phase of said composition, and (d) from about 0.1 to about 15 weight percent based on the dry weight of said composition of a compound having the formula wherein R1, R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said compound in solid solution with the continuous phase of said composition, said aromatic radical containing about 4 to 14 carbon atoms in the aromatic ring thereof.
3. 3. A photoconductive composition as described in claim 2 wherein said carbonate polymer contains the following moiety in a recurring unit:
   
   wherein:
   each of R9 and R10, when taken separately, is selected from the group consisting of a hydrogen atom, an alkyl radical of from 1 to about 10 carbon atoms, and a phenyl radical, and R9 and R10, when taken together, are the carbon atoms necessary to form a cyclic hydrocarbon radical, the total number of carbon atoms in Rg and R9 being up to 19; and R8 and R11 are each selected from the group consisting of hydrogen, alkyl radicals of from 1 to about 5 carbon atoms, alkoxy radicals of from 1 to about 5 carbon atoms and a halogen atom.
4. 4. An aggregate photoconductive composition comprising (a) a continuous electrically insulating carbonate polymer phase, said polymer having an alkylidene diarylene moiety in a recurring unit, (b) a discontinuous phase comprising a co-crystalline complex of (i) a 2,4,6-substituted thiapyrylium dye salt and (ii) a carbonate polymer having an alkylidene diarylene moiety in a recurring unit, said discontinuous phase dispersed in said continuous phase, (c) from about 25 to about 40 weight percent based on the dry weight of said composition of at least one non-blue light absorbing organic photoconductor in solid solution with the continuous phase of said composition, and (d) from about 5 to about 10 weight percent based on the dry weight of said composition of a compound having the formula wherein R1 R2, R3, and R4 are each selected from the group consisting of an aryl radical and an alkyl radical, Ar1 and Ar3 are each selected from the group con-sisting of an unsubstituted phenyl radical and a substituted phenyl radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, and Ar2 is an unsubstituted carbocyclic aromatic radical or a substituted carbocyclic aromatic radical having an alkyl, aryl, alkoxy, aryloxy, or halogen substituent, said compound in solid solution with the continuous phase of said composition, said aromatic radical containing about 4 to 14 carbon atoms in the aromatic ring thereof.
5. 5. An aggregate photoconductive composition as described in claim 4 wherein R1 R2, R3, and R4 are each phenyl radicals or alkyl-substituted phenyl radicals and Ar2 is a phenyl radical or an alkyl-substituted phenyl radical, said alkyl substituents having l or 2 carbon atoms.
6. 6. An aggregate photoconductive composition as described in claim 4 wherein said compound is selected from the group consisting of 4-diphenylamino-4'-[4-(diphenylamino)styryl]stilbene; 4-di-(p-tolylamino)-4'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2', 3',5',6'-tetramethyl-4'-[4-(di-p-tolylamino)styryl]stilbene;
   4-di-(p-tolylamino)-2'-[4-(di-p-tolylamino)styryl]stilbene; 4-di-(p-tolylamino)-2',4'-dimethyl-5'-[4-(,di-p-tolylamino)styryl]-stilbene; and 1,4-bis(4-N-ethyl-N-p-tolylaminostyryl)benzene.
7. 7. An aggregate photoconductive composition as described in claim 4 wherein said organic photoconductor is a polyarylalkane photoconductor or an arylamine photoconductor.
8. 8. An aggregate photoconductive composition as described in claim 4 wherein said organic photoconductor is a polyarylalkane photoconductor.
9. 9. In an electrophotographic element comprising a conductive support and a photoconductive layer coated over said support, the improvement wherein said photoconductive layer comprises the photoconductive composition of claim 1.
10. 10. In an electrophotographic element comprising a conductive support and a photoconductive layer coated over said support, the improvement wherein said photoconductive layer comprises the photoconductive composition of claim 4.
11. 11. In an electrophotographic process wherein an electrostatic charge pattern is formed on a photoconductive element comprised of an electrically conducting support having coated thereover a layer of a photoconductive composition, the improvement wherein said photoconductive composition is a com-position as described in claim 4.